How do I check if an app is a non-system app in Android?

I was under the impression that all apps in the system image are system apps (and normally installed in /system/app).

If FLAG_SYSTEM is only set to system applications, this will work even for apps in external storage:

boolean isUserApp(ApplicationInfo ai) {
    int mask = ApplicationInfo.FLAG_SYSTEM | ApplicationInfo.FLAG_UPDATED_SYSTEM_APP;
    return (ai.flags & mask) == 0;
}

An alternative is to use the pm command-line program in your phone.

Syntax:

pm list packages [-f] [-d] [-e] [-s] [-3] [-i] [-u] [--user USER_ID] [FILTER]

pm list packages: prints all packages, optionally only
  those whose package name contains the text in FILTER.  Options:
    -f: see their associated file.
    -d: filter to only show disbled packages.
    -e: filter to only show enabled packages.
    -s: filter to only show system packages.
    -3: filter to only show third party packages.
    -i: see the installer for the packages.
    -u: also include uninstalled packages.

Code:

ProcessBuilder builder = new ProcessBuilder("pm", "list", "packages", "-s");
Process process = builder.start();

InputStream in = process.getInputStream();
Scanner scanner = new Scanner(in);
Pattern pattern = Pattern.compile("^package:.+");
int skip = "package:".length();

Set<String> systemApps = new HashSet<String>();
while (scanner.hasNext(pattern)) {
    String pckg = scanner.next().substring(skip);
    systemApps.add(pckg);
}

scanner.close();
process.destroy();

Then:

boolean isUserApp(String pckg) {
    return !mSystemApps.contains(pckg);
}

You can check the signature of application which it signed with system. Like below

/**
 * Match signature of application to identify that if it is signed by system
 * or not.
 * 
 * @param packageName
 *            package of application. Can not be blank.
 * @return <code>true</code> if application is signed by system certificate,
 *         otherwise <code>false</code>
 */
public boolean isSystemApp(String packageName) {
    try {
        // Get packageinfo for target application
        PackageInfo targetPkgInfo = mPackageManager.getPackageInfo(
                packageName, PackageManager.GET_SIGNATURES);
        // Get packageinfo for system package
        PackageInfo sys = mPackageManager.getPackageInfo(
                "android", PackageManager.GET_SIGNATURES);
        // Match both packageinfo for there signatures
        return (targetPkgInfo != null && targetPkgInfo.signatures != null && sys.signatures[0]
                .equals(targetPkgInfo.signatures[0]));
    } catch (PackageManager.NameNotFoundException e) {
        return false;
    }
}

---

You can get more code on my blog How to check if application is system app or not (By signed signature)

PackageManager pm = mcontext.getPackageManager();
List<PackageInfo> list = pm.getInstalledPackages(0);

for(PackageInfo pi : list) {
    ApplicationInfo ai = pm.getApplicationInfo(pi.packageName, 0);

    System.out.println(">>>>>>packages is<<<<<<<<" + ai.publicSourceDir);

    if ((ai.flags & ApplicationInfo.FLAG_SYSTEM) != 0) {
        System.out.println(">>>>>>packages is system package"+pi.packageName);          
    }
}